Carotid (kuh-ROT-id) ultrasound is a safe, painless procedure that uses sound waves to examine the blood flow through the carotid arteries.

Your two carotid arteries are located on each side of your neck. They deliver blood from your heart to your brain.

Carotid ultrasound tests for blocked or narrowed carotid arteries, which can increase the risk of stroke. The results can help your doctor determine a treatment to lower your stroke risk.

A carotid ultrasound is performed to test for narrowed carotid arteries, which increase the risk of stroke.

Carotid arteries are usually narrowed by a buildup of plaque — made up of fat, cholesterol, calcium and other substances that circulate in the bloodstream. Early diagnosis and treatment of a narrowed carotid artery can decrease stroke risk.

Your doctor will recommend carotid ultrasound if you have transient ischemic attacks (TIAs) or certain types of stroke and may recommend a carotid ultrasound if you have medical conditions that increase the risk of stroke, including:

• High blood pressure
• Diabetes
• High cholesterol
• Family history of stroke or heart disease
• Recent transient ischemic attack (TIA) or stroke
• Abnormal sound in carotid arteries (bruit), detected by your doctor using a stethoscope
• Coronary artery disease

To screen for narrowed or blocked blood vessels in other areas of the body, you may need additional tests, including:

• Abdominal ultrasound. You may have an abdominal ultrasound to test for conditions affecting the blood vessels or organs in your abdominal area.
• Ankle-brachial index test. This test measures and compares the blood pressure between your ankle and your arm. The test shows reduced or blocked blood flow to your legs.
• Cardiac stress test. This test shows how well your heart performs when under stress, such as during exercise. Results can indicate poor blood flow to the heart.

Your doctor may also order imaging tests to detect coronary artery disease.

Other uses of carotid ultrasound

Your doctor may order a carotid ultrasound to:

• Evaluate blood flow through the artery after surgery to remove plaques (carotid endarterectomy)
• Evaluate the placement and effectiveness of a stent, a mesh tube used to improve blood flow through an artery
• Locate a collection of clotted blood (hematoma) that may prevent blood flow
• Detect other carotid artery abnormalities that may disrupt blood flow

You can take the following steps to prepare for your appointment:

• Call the day before the exam to confirm the time and location of the exam.
• Wear a comfortable shirt with no collar or an open collar.
• Don't wear a necklace or dangling earrings.

Unless your doctor or the radiology lab provides special instructions, you shouldn't need to make any other preparations.

How it works

A technician (sonographer) conducts the test with a small, hand-held device called a transducer. The transducer emits sound waves and records the echo as the waves bounce off tissues, organs and blood cells.

A computer translates the echoed sound waves into a live-action image on a monitor. The radiologist may use a Doppler ultrasound, which shows blood flowing through the arteries. In a Doppler ultrasound, the rate of blood flow is translated into a graph.

A carotid ultrasound usually takes about 30 minutes.

During the procedure

You'll likely lie on your back during the ultrasound. The ultrasound technician (sonographer) may position your head to better access the side of your neck.

The sonographer will apply a warm gel to your skin above the site of each carotid artery. The gel helps transmit the ultrasound waves back and forth. The sonographer then gently presses the transducer against the side of your neck.

You shouldn't feel any discomfort during the procedure. If you do, tell the sonographer.

A doctor who specializes in imaging tests (radiologist) will review your test results, then prepare a report for the doctor who ordered the test. This may be your primary care doctor, a doctor trained in heart and blood vessel conditions (cardiologist), or a doctor trained in brain and nervous system conditions (neurologist).

The radiologist may also discuss the results of the test with you immediately after the procedure.

The doctor who ordered the test will explain to you what the carotid ultrasound revealed and what that means for you.

If the test reveals you're at risk of a stroke, your doctor may recommend the following therapies, depending on the severity of blockage in your arteries:

• Eat a healthy diet, including fruits, vegetables and whole-grain breads and cereals, and limit saturated fat.
• Exercise regularly.
• Keep a healthy weight.
• Don't smoke and avoid secondhand smoke.
• Take medications to lower blood cholesterol and blood pressure.
• Take medications to prevent blood clots.
• Have a surgical procedure to remove carotid artery plaques (carotid endarterectomy).
• Have a surgical procedure to open up and support your carotid arteries (carotid angioplasty and stenting).

If your doctor ordered the carotid ultrasound as a follow-up to a surgical procedure, your doctor can explain whether the treatment is working, and whether you'll need additional treatment or follow-up exams.

Additional tests

If your results are unclear, your doctor may order additional imaging tests, including:

• Computerized tomography angiogram (CTA) scan. A CTA scan uses a series of X-rays to produce detailed images of the blood vessels in your body. Your doctor may inject a dye into a vein to highlight your carotid arteries.
• Magnetic resonance imaging (MRI). An MRI uses a magnetic field and radio waves to produce detailed images of soft tissues in your body. A magnetic resonance angiography (MRA) scan also may be performed to get a better look at blood vessels.